// TODO: 定义宏生成如下结构  
// #[derive_hash(Block)]  
// struct Block { data: String, prev_hash: String }  
// 宏应自动实现 fn hash(&self) -> String  

#[test]  
fn test_block_hash() {  
    let block = Block { data: "Genesis".into(), prev_hash: "0".into() };  
    assert!(!block.hash().is_empty());  
}  